Well installations and improved tubing therefor



Feb. 13, 1962 J. 1.. HOLMQUIST WELL INSTALLATIONS AND IMPROVED TUBINGTHEREFOR 2 Sheets-Sheet 1 Filed Feb. 5, 1958 PEL '47? VELy A/O/V-COMP/76777545 FOQMIQT/ON BENTON/77C 5/1045 F/nasr COMP/767795 P52 07/V62 Y NON-(015194654525 FORMAT/0N Sc-(a/va (UMP/9677751. E FORM/7770 AINVENTOR .105 L fibLMQI/IJI ATTORNEY Feb. 13, 1962 J. L. HOLMQUIST WELLINSTALLATIONS AND IMPROVED TUBING THEREFOR 2 Sheets-Sheet 2 Filed Feb.3, 1958 0! M m M M ATTORNEY around the casing.

.formation. mation overlies the compacting formation, the overlying [Uite States Patent 3,020,962 WELL INSTALLATIONS AND IMPROVED TUBINGTHEREFOR John L. Holmqnist, Aliquippa, Pa., assignor, by mesneassignments, to Armco Steel Corporation, Middletown,

Ohio, a corporation of Ohio Filed Feb. 3, 1958, Ser. No. 712,879 6Claims. (Cl. 166242) This invention relates to deep well installationsfor producing oil and other fluids from underground formations, andparticularly to apparatus useful in connection with such installationswherein the bore hole traverses a formation subject to being compactedby reason of the Weight of earth above the formation.

In modern oil field practice, it is common for a single formation to betapped by a number of wells. Considering a given producing well or borehole, the same may traverse one such formation, extending therebelow, ormay terminate therein. Many formations are of such porous nature that,as fluid is withdrawn therefrom, the weight of the overlying earthcauses the formation to be progressively collapsed or compacted. Thisphenomena has heretofore caused considerable difficulty in oil fielwork.

In most instances involving a compactable formation traversed by a easedbore hole, the casing is gripped tightly by the compacting formation,less tightly by the non-compacting formation. It appears that, in thenoncompacting formations, there is relatively less tendency for thematerial of the formation to slough off and pack In the compactingformation, however, there is a marked sloughing off of material and thismaterial becomes so tightly packed about the casing that there is greatfrictional resistance to relative movement between the compactingformation and the casing. When the formation compacts, due to loss offluid therefrom, the portion of easing traversing the compactingformation is subjected to a large, progressive, axial compressive force,since the material of the compacting formation cannot slide along thesurface of that casing portion. If no special provisions are made toaccommodate such force, the result will be a severe distortion of thecasing portion to which the force is applied. This distortion willusually be of such nature as to decrease the effective inner diameter ofthe casing portion, so that well tools cannot be passed therethrough,and the casing must therefore be repaired.

While primarily concerned with situations of the type just referred to,it is also contemplated that the invention r will be applicable tosituations where, because of the nature of the particular earthformations involved, the casing will be tightly gripped by thenon-compacting formations and less tightly gripped by the compacting Inthat event, when a non-compacting forformation will sink as compactingof the lower formation occurs. Sinking of the overlying formation tendsto force the casing downwardly. Then, assuming the casing to be firmlyheld below the compacting formation,

that portion of the casing extending through the compacting formationwill be subjected to an axial compressive force increasing in magnitudeas the overlying formation sinks.

Thus, in both of the situations referred to, that portion of the casingwhich traverses the compacting formation is subjected to a compressiveforce resulting from subsidence of that formation, and, if there issuflicient subsidence, distortion of the casing will result. Insofar asI have been able to determine, no satisfactory method for preventingsuch deformation has heretofore been proposed.

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It is accordingly the general object of the present invention to providean improved apparatus for preventing or minimizing destructivedeformation of well casing extending through a relatively highlycompactable formation.

Another object of the invention is to provide a deep well installationwherein the well casing structure is so constructed and arranged thatthe portion thereof traversing a compactable earth formation is capableof being axially distorted, as the earth formation compacts or subsides,without decreasing the internal diameter of the casing in such area, andwithout causing the casing to be laterally deformed.

A further object of the invention is to provide a novel Well casingstructure for such use.

In order that these and other objects of the invention may be understoodin detail, reference is had to the accompanying drawings, which form apart of this specification, and wherein:

FIG. 1 is a diagrammatic illustration of two Wells drilled in an areawhere there is a formation subject to being compacted as fluid iswithdrawn therefrom;

FIG. 2 is an elevational view of a portion of a length of well casingconstructed in accordance with one embodiment of the invention;

FIG. 3 is an elevational view of a portion of a lengt of well casingconstructed in accordance with another embodiment of the invention;

FIG. 4 is a detail longitudinal sectional view taken through a portionof the well casing structure of either FIG. 2 or FIG. 3, the sectionbeing taken axially of the casing;

FIGv 5 is a view like FIG. 6, illustrating the manner in which thecorrugations provided in accordance with the invention flatten, undercompressive forces directed axially of the well casing, to allowshortening of the casing without substantial decrease in the internaldiameter thereof;

FIG. 6 is an elevational view of a portion of well casing constructed inaccordance with a further embodiment of the invention, and

FIG. 7 is a detailed fragmentary transverse sectional view, on anenlarged scale, taken through the Well casing of FIG. 5, andillustrating the manner in which portions of such well casing areperforated to allow fluid to enter the casing.

The problem to which the invention is directed will be apparent fromFIG. 1, where A represents an oilbearing formation and B represents asecond oil-bearing formation lying above and spaced from formation A.Between formations A and B is an intervening .earth formation C.Formation B is overlain by earth formation D. Assuming that theformations A and B are relatively h'ghly porous, it will then beunderstood that, as oil is Withdrawn therefrom, the formations A and Bwill be progressively compressed or compacted by reason of the greatweight of the overlying earth formations.

In the usual situation to which the invention will be applied, thecompactable formation or formations will comprise alternate layers ofoil' sand which, relatively speaking, is not highly compactable, and ahighly compactable material such as bentonitic shale, as indicated bythe legends in FIG. 1. Where the compacting layers are of bentonit'cshale, such layers will have a total subsidence, as the water of suchlayers is lost to the bore hole, of about 10%. The compactable formationconsisting of about 50% oil sand and 50% bentonitic shale, the ultimatedecrease in thickness of the comthat the amount of oil withdrawn fromthe formations is relatively large, over a given period, even though thewells are operating under legal production limitations. Thus, theformation B may be tapped by a first well established by drilling a borehole into formation B and lining the same with a well casing 1 having anupper portion 1 disposed above formation B and a lower portion 1disposed in the formation B.

A second well may tap formation A alone, or may tap both formations Aand B. This well may be provided by drilling a bore hole to formation Aand lining the same with casing 2 comprising a portion 2 extendingdownwardly to formation B, an intermediate portion 2 traversingformation B, a second intermediate portion 2 extending downwardly toformation A and a lower end portion 2 disposed in formation A.

In accordance with the invent'on, the well casing portions 1, 2 and 2are of plain, conventional lengths of plain well casing engagedrelatively loosely by the surrounding earth. Casing portions 1 2 and 2on the other hand, are so constructed as to be capable of shorteningunder the axial compression forces applied thereto as formations A and Bsubside. This is accompl'shed by providing these casing portions withtransversely disposed corrugations extending outwardly of the wall ofthe casing.

Thus, as seen in FIG. 2, casing portions 1 2 and 2 may comprise lengthsof casing made up of alternate plain cylindrical sections 3 andcorrugated sections 4 connected in end-to-end relation by circular postwelds 5. In this embodiment, the corrugat'ons 6 of sections 4 are eachcomplete circles disposed in spaced planes lying at right angles to theaxis of the length of easing.

Alternatively, as seen in FIG. 3, the corrugations 6' of sections 4 canbe of helical configuration. In either case, the corrugations havesemi-circular cross-sect'ons and extend wholly outwardly of the innersurface of the casing, no portion of the corrugation extending inwardlyof the casing.

Advantageously, the corrugations have a wall thickness materially lessthan the plain portions disposed between the corrugations. Suchdilference in th ckness is illustrated in FIG. 4. Thus, it isadvantageous to have the wall thickness of the corrugations slightlymore than one-half that of the casing portions lying between adjacentcorrugations. By making the walls of the corrugations thinner than theadjacent plain portions of the sect'ons 4, 4, greater assurance is hadthat shortening of the sections 4, 4' under compressive load will occursubstantially entirely because of deformation of the corrugations, therebeing no inward buckling of the main, cylindrical wall. In normalpractice, it is advantageous to have the wall thickness of plainsections 3 equal to the wall thickness of the sections between thecorrugations, though it will be understood that sections 3 may havethicker walls.

Since the corrugations are disposed wholly outwardly of the innersurface of the casing, forces applied axially to the casing do notresult in any material change in the inner diameter of the casing. Thus,assum'ng that the casing portion illustrated in FIGS. 2, 3 is subjectedto axial compression, the corrugations tend to collapse or flatten, asillustrated in FIG. 5, substantially without bending or canting of theintermediate plan portions. In FIG. 5, it will be noted that collapse orflattening of the corrugations does not cause any portion of the casingwall to project inwardly of the casing. This is in sharp contrast to theresults obtainable with more conventional corrugations wherein thecorrugations corresponding to those seen at 6, 6 would be separated byinwardly directed corrugations.

The manner of constructing the first well assembly mentioned inconnection with FIG. 1 is illustrated by an actual installation made atLake Maracaibo, Venezuela. The bore hole was conventionally drilledthrough the overlying earth D to the surface for formation B. This borehole portion was then lined with conventional, plain, tubular, 7" wellcasing inthe usual manner. Using a 6 /4 bit lowered through the casingportion 1 so established, the bore hole was then further drilled toextend to the bottom of formation B, and the drill string re moved.Lengths of casing connected together to form casing portion 1 were thenlowered through the cas'ng portion 1 As indicated in FIG. 6, such casinglengths were made up of alternate plain sections 3 and corrugatedsections 4 welded together in end-to-end relation. A packer (not shown)was provided at the top of casing portion 1 to seal the same to casingportion 1 in fluidt'ght relation, casing portion 1 thus being hung fromportion I by means of the packer.

Since this well assembly was to produce from formation B, the interiorof casing portion 1 was placed in communication with the formation byproviding transversely disposed, longitudinally spaced slots 7 in theplain portions 3. As seen in FIG. 7, such slots were provided by makingcircular cuts in the casing wall from I both the inside and the outside,these cuts being deep enough to combine to form the desired casingperforation.

In the particular application of the invention referred to, the totaldepth of the well was appoximately 4,500 ft. In this application, it wasfound that the corrugated casing sections, having an outside diameter of5 passed readily through the bore hole extension provided by the 6%.bit. Depending upon the particular formation, the bore hole extensionmay be under-reamed to provide more space for the corrugated sections.

Since a considerable amount of well casing comprising corrugatedsections will normally be employed in each well, numerous sections ofthe corrugated well casing are assembled by means of conventionalthreaded couplings 8, FIG. 6.

When the casing portions 1 and 1 were in place, a 3" tubing was run downthe casing and a production packer employed to seal off the spacebetween the tubing and well casing, additional 3" tubing then being runto the tubing head from the production packer, and oil was produced fromformation B by means of the tubing in the usual manner.

When faced with a situation such as presented by the Lake Maracaibo welljust discussed, the use of conventional telescopic slip joints to allownon-destructive shortening of the casing might be contemplated. Suchdevices are unsatisfactory, however, for a number of reasons. The mostimportant of these is the fact that use of slip joints would provide acapacity for shortening of the casing only at relatively widely spacedpoints, there being little chance that, when the casing was in the borehole, these spaced points would be at the level of the bentonitic shale,rather than at the level of the oil sand. This disadvantage is overcomein accordance with the invention because the corrugations in effectprovide in casing a capacity for shortening thereof throughout thatportion of the casing which traverses the compacting formation. Thespacing between corrugated sections 4, 4 is sufficiently small to assurethat the casing will always have capacity for shortening at the level ofthe bentonitic shale. Further advantages are obtainable in accordancewith the invention by making that portion of the casing which traversesthe compacting formation entirely of corrugated sections 4, 4.

In situations where the bore hole extends not only through the formationB but also therebelow to the second formation A, the procedure forestablishing the bore hole and lining the casing is substantially thesame as just described. In such cases, however, intermediate casingportion 2 can be either unperforated, as indicated in FIGS. 2 and 3 orperforated in the manner described with reference to casing portion 1FIG. 6. Referring again to FIG. 6, it will be noted that theperforations 7 are provided in the plain sections of the lengths ofcause the relatively thicker plain walls can accommodate theperforations with less danger of weakening and attendant deformation.

The embodiments of the invention here illustrated are illustrative, andit will be understood that various modifications can be employed withoutdeparting from the scope of the appended claims. Thus, while it isadvantageous to employ alternate plain sections 3, disposed between thecorrugated sections, the lengths of casing can be corrugated throughout.

Where the term corrugation is employed herein, it is used to connote notonly the independent, circular corrugations of FIG. 2, but also theadjacent turns of the continuous helical corrugations of FIG. 3.

What is claimed is:

1. In a deep well installation for producing fluid from an undergroundearth formation subject to being compacted as fluid is withdrawntherefrom, the combination of a casing lining said borehole andincluding a lower portion extending into said formation and an uppersection extending through the earth overlying said formation, said lowercasing portion being so tightly gripped by said compactable earthformation that relative movement between said formation and lower casingportion is substantially precluded as said formation is compacted duringwithdrawal of fluid therefrom, said lower casing portion comprisingalternate plain and transversely corrugated sections, said corrugatedsections including transversely disposed corrugations extending whollyoutwardly from the casing, said corrugations each having a wallthickness substantially less than the casing proper and being effectiveto allow said intermediate casing portion to shorten, substantiallywithout decrease in the inner diameter thereof, as said formation iscompacted.

2. A deep well installation in accordance with claim 1 and wherein saidplain portions are perforated.

3. In a deep well installation for producing fluid via a borehole whichtraverses an underground earth formation subject to being compacted bythe weight of overlying earth, the configuration of plain well casingportions lining said borehole above and below said formation, anintermediate well casing portion lining said borehole in the areathereof traversing said' formation, said intermediate well casingportion being so tightly gripped by said formation that relativemovement between said' formation and intermediate casing portion as saidfor-- mation is compacted is substantially precluded, said intermediatecasing portion comprising alternate plain and transversely corrugatedsections, said corrugated sections including transversely disposedcorrugations extending wholly outwardly therefrom, said corrugationseach having a wall thickness substantially less than the casing properand being effective to allow said intermediate casing portion toshorten, substantially without decrease in the inner diameter thereof,as said formation is compacted, and a lower end casing portion providedwith means for entry of fluid to the casing.

4. A deep well installation in accordance with claim 3 and wherein saidplain sections of said intermediate casing portion are perforated toallow fluid to enter the casing from said formation.

5. As a new article of manufacture, a length of well casing comprisingalternate plain and transversely corrugated cylindrical tubular sectionsjoined in end-to-end relation by circular weld-s, the corrugations ofsaid transversely corrugated sections extending wholly outwardly of saidlength of casing, said corrugations being separated by cylindricalportions which are thicker walled than the walls of said corrugationsand of smaller diameter than the diameter of said corrugations but equalto the diameter of the plain cylindrical tubular sections and beingeffective to allow axial distortion of said length of casingsubstantially without decrease in the inner diameter thereof.

6. A length of well casing constructed in accordance with claim 5 andwherein said plain sections are perforated.

References Cited in the file of this patent UNITED STATES PATENTS1,055,674 Smith Mar. 11, 1913 1,330,316 Hall Feb. 10, 1920 1,644,823 FayOct. 11, 1927 1,879,663 Dreyer Sept. 27, 1932 2,712,854 Creighton July12, 1955 2,758,612 Zaleski Aug. 14, 1956

